Since World War II the chemical industry has grown to the point where there are over 35 million metric tons of obnoxious or hazardous wastes being generated. Large quantities of these wastes contain synthetic halogenated materials such as found in dielectric fluids, flame retardants, refrigerants, heat transfer fluids, lubricants, protective coatings, pesticides, including herbicides and insecticides. Furthermore, it is well knon that both the petroleum industry and the coal industry contribute many more millions of metric tons of hazardous chemical wastes to be disposed of which contain obnoxious organic compounds. Many of these materials are non biodegradable or recalcitrant, i.e. difficult to biodegrade.
In many cases, these materials and the by-products or residues from their manufacture have been accumulated in landfills or discharged (treated or partially treated) into the conduits of municipal sewer systems. In the case of landfills and over the course of time, and by a process of liquifaction the contents of the landfill ultimately produces a leachate which must be disposed of.
In the case of disposing of chemical waste effluents into the municipal systems, the chemical waste effluents are mixed and diluted into the municipal wastes and they become contaminants which are difficult or impossible for the municipal wastewater treatment plants to handle in a way which meets the standards of disposal of such effluents and the sludges produced, set up by the Federal and State governments. In some cases the toxic chemicals pass thru the municipal wastewater treatment system and show up "untreated" in the waste sludge and waste effluents.
All kinds of methods and techniques have been proposed and used for disposing of and/or treating these chemical wastes and their byproducts to make them compatible with the environment. In spite of all the effort and money being spent, no technology has evolved which is economically and technically satisfactory.